Prims

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This article is about primitives. For LSL related information, see Category:LSL Prim.


Introduction

This page is mostly about how primitives are implemented in the server and viewer code. It might help users of the in-world build tool understand the use of the many options. An excellent detailed summary can be found here. [1]

Primitives in Second Life are constructed by starting with a basic two dimensional shape, modifying it, and extruding it in to the third dimension along a path while applying modifications to the extrusion. The most basic example is a cube which starts out as a 2D square and extrudes along a linear path with no modifications to make a cube. A cylinder starts out as as circle and extrudes along the same linear path. If the circle was extruded along a circular path you would create a torus, and if a half-circle is extruded along another type of circular path you create a sphere.

2D Shape (Profile)

  • ProfileCurve
    • Two combined enums: the lower 4 bits define the outer profile shape, and the high 4 bits define the type of hole if ProfileHollow is non-zero
Profile Shape:
Circle = 0x00
Square = 0x01
Isometric Triangle = 0x02
Equilateral Triangle = 0x03
Right Triangle = 0x04
Half Circle = 0x05
Hole Shape:
Same = 0x00
Circle = 0x10
Square = 0x20
Triangle = 0x30

2D Shape (Profile) Modifications

  • ProfileBegin
    • Where the cut (if any) in the profile begins
  • ProfileEnd
    • Where the cut (if any) in the profile ends
  • ProfileHollow
    • How much of the profile is hollowed out, as a percent of the original bounding box. If non-zero this creates a hole using the shape defined in the higher bits of ProfileCurve

Extrusion (Path)

  • PathCurve
    • Enum for the extrusion path. For whatever reason only the upper bits are used in this field:
Line = 0x10
Circle = 0x20
Circle2 = 0x30
Test = 0x40 // ???
Flexible = 0x80

Extrusion (Path) Modifications

  • PathBegin
  • PathEnd
  • PathScaleX
  • PathScaleY
  • PathShearX
  • PathShearY
  • PathTwistBegin
  • PathTwist
  • PathRadiusOffset
  • PathTaperX
  • PathTaperY
  • PathRevolutions
  • PathSkew